Purpose:
MacTel is a slowly progressing disease of the macula where both vascular and neuronal layers of the retina are involved. There is currently no known safe and effective treatment for MacTel. The CNTF Phase 1 trial is a non-randomised uncontrolled trial that has completed 3 years of safety follow-up. The purpose of this study is to describe the imaging safety outcomes at 36-months as per independent and objective Reading Centre (RC) evaluation where all personnel are masked to the treatment status of the participants’ eyes.

Methods:
One eye (eye with worse visual acuity) of each patient was implanted and the patients were followed up biannually, the most recent of which is the 3-year follow-up. After clinical examination and electrodiagnostics, standard imaging battery including colour fundus photography, fluorescein angiogram, optical coherence tomography, fundus autofluorescence imaging and microperimetry were carried out on both eyes. The deidentified images were sent to the RC at Moorfields Eye Hospital, London, UK where the images were read by masked trained and certified MacTel graders.

Results:
Seven participants were enrolled (2 males; 48-67 years of age). None had neovascular stage MacTel at enrolment or at 36-months. On image analysis, there was no significant progression of any MacTel related characteristics (opacification of the retina, telangiectasias, blunted vessels, pigmentary changes) in either eye of the participants. The mean retinal thickness in eyes with CNTF implant showed a marked increase in ETDRS zones 6-9 (20-23 micron), while the untreated eyes showed minimal increase of 6-11 micron. On en-face imaging, the main break area did not change in either eye significantly (mean difference in area -0.04±0.07; 95%CI: -0.22-0.16; p=0.58). Microperimetry showed no statistically significant difference between the mean change in sensitivity from baseline to 36-months between eyes (mean±SE difference=0.9±0.5 dB; 95%CI:-0.3-2.2; p=0.12), and this level of change is within the expected level of variability for this test modality.

Conclusions:
So far there has been no safety issue identified on any imaging modalities used for this trial. A Phase 2 trial is ongoing to establish efficacy of CNTF in MacTel.